Optimization of semen cryopreservation in black-footed (Spheniscus demersus) and gentoo (Pygoscelis papua) penguins using dimethylacetamide and dimethylsulfoxide.

Black-footed penguins (Spheniscus demersus) are classified as endangered, and the populations of gentoo penguins (Pygoscelis papua) are rapidly decreasing. The optimization of semen cryopreservation in these species, for preserving their genetic diversity in genome resource banks, is essential for the success of captive breeding programs. This study compares the effectiveness of two permeating cryoprotectants, dimethylacetamide (DMA) and dimethylsulfoxide (DMSO), on frozen-thawed sperm characteristics. Semen samples were collected during each breeding season once a week during two consecutive years. Semen samples were packaged in 0.25 ml straws and frozen by placing them in nitrogen vapors. After thawing, sperm motility characteristics were examined by computer-assisted sperm analysis. Propidium iodide and SYBR-14 were used as fluorochromes for the examination of membrane integrity. DNA integrity was evaluated by TUNEL assay. Gentoo sperm characteristics after freeze-thawing did not show any differences when using DMSO or DMA. In black-footed samples, progressive motility, curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity (VAP), linearity (LIN), and straightness (STR) were greater using 8% DMSO (P < 0.05) than 6% DMA. The cryoresistance ratio (CR) using 8% DMSO was greater (P < 0.05) in gentoo than black-footed samples for CR-VCL and CR-VAP, and 6% DMA returned greater CR values (P < 0.05) than in black-footed samples for all characteristics evaluated. No differences were found in DNA fragmentation. In conclusion, the present results highlight the benefits of using 8% DMSO compared to 6% DMA in penguins. Sperm from black-footed showed a higher sensitivity to freezing-thawing process than gentoo sperm.

Impact of fertilisation practices on soil respiration, as measured by the metabolic index of short-term nitrogen input behaviour.

The main objective of this study was the evaluation of the impact of different sources of organic waste (used as an N source) on soil quality (as measured by CO(2) release) and N transformation processes (available inorganic N forms) in a short-term field study of an almond tree plantation. Three compost types were used as organic fertilisers: EC compost constituted from organic agriculture farm (vegetables and manure), SC compost formed from sewage sludge and pruning waste composted, and XC compost comprised a mixture of composted sewage sludge plus slurry and manure from an intensive pig farm. The two compost doses were compared according to N content, and a high dose (H), corresponding to 210 kg N ha(-1), and a low dose (L), equivalent to 105 kg N ha(-1), were used. In addition, an N rate corresponding to 130 kg N ha(-1), which resulted from the supplementation of NPK mineral fertiliser with compost application at a low dose (mixed fertilisation), was compared in a parallel study. Generally, almost all organically treated soils demonstrated an improvement in the levels of C, N and P, compared to controls (unfertilised soils). In addition, the nitrate content increased, predominating over ammonium content, with the highest values in the soils with the low dose application of SC. Furthermore, soil respiration improved in organically treated soils, which showed different responses according to the organic-exogenous source of the incorporated matter. In contrast, a mineral supplement promoted a decrease in biological activity and resulted in lower CO(2) production in soils with XC and mineral fertiliser. Contrary to the organically treated soil, in soils with mix fertilisation the NH(4)(+)-N was the primary available form of nitrogen. However, the application of SC plus mineral fertiliser to soil caused a positive effect on CO(2) emissions compared to the control soil. Soil respiration behaviour was closely related to the form of inorganic N available in the soils due to the fertilisation practice type (organic or mixed), where both parameters seemed to depend on the mobilisations of cations (Na(+) and Ca(2+)) to the soil solution.